A vessel filter is a device inserted into a blood vessel to capture particles in the blood flow. Typically the device is inserted into a major vein to prevent a blood clot from reaching the lungs. Patients, who have recently suffered from trauma, have experienced a heart attack (myocardial infarction), or who have undergone major surgical procedure (e.g., surgical repair of a fractured hip, etc.) may have thrombosis in a deep vein. When the thrombus clot loosens from the site of formation and travels to the lung, it may cause pulmonary embolism, a life-threatening condition. A vessel filter may be placed in the circulatory system to intercept the thrombi and prevent them from entering the lungs.
Examples of various blood vessel filters and delivery systems are disclosed in U.S. Pat. No. 5,300,086, titled “DEVICE WITH A LOCATING MEMBER FOR REMOVABLY IMPLANTING A BLOOD FILTER IN A VEIN OF THE HUMAN BODY” issued to Gory et al., dated Apr. 5, 1994; U.S. Pat. No. 5,350,398, titled “SELF-EXPANDING FILTER FOR PERCUTANEOUS INSERTION” issued to Pavcnik et al., dated Sep. 27, 1994; U.S. Pat. No. 5,531,788, titled “ANTI-PULMONARY EMBOLISM FILTER” issued to Dibie et al., dated Jul. 2, 1996; U.S. Pat. No. 5,720,764, titled “VENA CAVA THROMBUS FILTER” issued to Naderlinger, dated Feb. 24, 1998; U.S. Pat. No. 5,836,969, titled “VENA CAVA FILTER” issued to Kim et al., dated Nov. 17, 1998; U.S. Pat. No. 5,954,741 titled “VENA-CAVA FILTER” issued to Fox, dated Sep. 21, 1999; U.S. Pat. No. 6,059,825, titled CLOT FILTER issued to Hobbs et al., dated May 9, 2000; U.S. Pat. No. 6,126,673, titled “VENA CAVA FILTER” issued to Kim et al., dated Oct. 3, 2000; U.S. Pat. No. 6,080,178, titled “VENA CAVA FILTER” issued to Meglin, dated Jun. 27, 2000; U.S. Pat. No. 6,251,122 B1, titled “INTRAVASCULAR FILTER RETRIEVAL DEVICE AND METHOD” issued to Tsukernik, dated Jun. 26, 2001; U.S. Pat. No. 6,258,026 B1, titled “REMOVEABLE EMBOLUS BLOOD CLOT FILTER DELIVERY UNIT” issued to Ravenscroft et al., dated Jul. 10, 2001; U.S. Pat. No. 6,391,045 B1, titled “VENA CAVA FILTER” issued to Kim et al., dated May 21, 2002; U.S. Pat. No. 6,436,120 B1, titled “VENA CAVA FILTER” issued to Meglin, dated Aug. 20, 2002; U.S. Pat. No. 6,468,290 B1, titled “TWO-PLANAR VENA CAVA FILTER WITH SELF-CENTERING CAPABILITIES” issued to Weldon et al., dated Oct. 22, 2002; U.S. Pat. No. 6,582,447 B1, titled “CONVERTIBLE BLOOD CLOT FILTER” issued to Patel et al., dated Jun. 24, 2003; U.S. Pat. No. 6,652,558 B2, titled “CONVERTIBLE BLOOD CLOT FILTER” issued to Patel et al., dated Nov. 25, 2003; each of which is incorporated herein by reference in its entirety.
Typically, the filter includes a plurality of radially expandable legs that support one or more filter baskets having a conical configuration. The device is configured for compression into a small size to facilitate delivery into a vascular passageway and is subsequently expanded into contact with the inner wall of the vessel. The device may later be retrieved from the deployed site by compressing the radially expanded legs and the associated baskets back into a small size for retrieval. The radially expandable legs may further include engagements for anchoring the filter in position within a blood vessel (e.g., vena cava). For example, the expandable legs may have hooks that can penetrate into the vessel wall and positively prevent migration of the filter in either direction along the length of the vessel. The body of the filter may include various biocompatible materials including compressible spring metals and shape memory materials to allow easy expansion and compression of the filter within the vessel. The hooks on the radially expandable legs may further include materials more elastic than the legs to permit the hooks to straighten in response to withdrawal forces to facilitate withdrawal from the endothelium layer without risk of significant injury to the vessel wall. The hooks may be formed on selected radially expandable legs, but not on others.
Many of the existing vena cava filters routinely encounter problems during retrieval. In addition, typical filters' deployment and retrieval are directionally dependent. For example, filters inserted using a femoral approach may require the retrieval to take place through a jugular approach. Accordingly, applicants recognize the desirability of a vena cava filter that can be easily retrieved independent of the orientation of the filter deployment within the vessel.